The role of miscibility in polymer:fullerene nanoparticulate organic photovoltaic devices

• P3HT:ICBA nanoparticle OPVs were fabricated and characterized.
• Power conversion efficiencies of 2.5% were obtained.
• Nanoparticle structure probed with synchrotron X-ray microscopy.
• Higher efficiency driven by improved miscibility of ICBA.

Polymer:fullerene blends are an attractive materials system for organic photovoltaic applications and conventionally are processed into thin films via chlorinated solvent based routes. Recently, the fabrication of OPV devices from water-dispersed nanoparticulate materials (solar paint) has attracted increasing interest since it offers the potential of morphological control coupled with device processing in the absence of an organic solvent. However, to date there have been no studies of the effect of different acceptors in the nanoparticle structure. In this letter, we report the performance of nanoparticulate organic photovoltaic (NPOPV) devices fabricated from poly(3-hexylthiophene) (P3HT):indene-C60-bisadduct (ICBA) blends. These devices exhibit power conversion efficiencies of 2.5%, which is the highest so far reported for NPOPV cells. Using a combination of scanning transmission X-ray microscopy and thermodynamic modelling we show that the improved performance is driven by the enhanced miscibility of ICBA in P3HT, which results in a more efficient intermixed structure in the annealed devices.

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